diff --git a/src/Trans.cpp b/src/Trans.cpp
index 28a05f05f9..774c7ac7ce 100644
--- a/src/Trans.cpp
+++ b/src/Trans.cpp
@@ -451,7 +451,7 @@ docstring const TransInitState::normalkey(char_type c)
 }
 
 
-docstring const TransInitState::deadkey(char_type c, KmodInfo d)
+docstring const TransInitState::deadkey(char_type c, KmodInfo const & d)
 {
 	deadkey_ = c;
 	deadkey_info_ = d;
@@ -488,7 +488,7 @@ docstring const TransDeadkeyState::normalkey(char_type c)
 }
 
 
-docstring const TransDeadkeyState::deadkey(char_type c, KmodInfo d)
+docstring const TransDeadkeyState::deadkey(char_type c, KmodInfo const & d)
 {
 	docstring res;
 
@@ -548,7 +548,7 @@ docstring const TransCombinedState::normalkey(char_type c)
 }
 
 
-docstring const TransCombinedState::deadkey(char_type c, KmodInfo d)
+docstring const TransCombinedState::deadkey(char_type c, KmodInfo const & d)
 {
 	// Third key in a row. Output the first one and
 	// reenter with shifted deadkeys
diff --git a/src/Trans.h b/src/Trans.h
index 61a57b8e1e..aefb4adff0 100644
--- a/src/Trans.h
+++ b/src/Trans.h
@@ -197,7 +197,7 @@ public:
 	///
 	virtual bool backspace() = 0;
 	///
-	virtual docstring const deadkey(char_type, KmodInfo) = 0;
+	virtual docstring const deadkey(char_type, KmodInfo const &) = 0;
 	///
 	static char_type const TOKEN_SEP;
 };
@@ -243,7 +243,7 @@ public:
 	///
 	bool backspace() override { return true; }
 	///
-	docstring const deadkey(char_type, KmodInfo) override;
+	docstring const deadkey(char_type, KmodInfo const &) override;
 };
 
 
@@ -260,7 +260,7 @@ public:
 		return false;
 	}
 	///
-	docstring const deadkey(char_type, KmodInfo) override;
+	docstring const deadkey(char_type, KmodInfo const &) override;
 };
 
 
@@ -281,7 +281,7 @@ public:
 		return false;
 	}
 	///
-	docstring const deadkey(char_type, KmodInfo) override;
+	docstring const deadkey(char_type, KmodInfo const &) override;
 };
 
 
@@ -335,7 +335,7 @@ public:
 	///
 	void translateAndInsert(char_type, Text *, Cursor &);
 	///
-	docstring const deadkey(char_type c, KmodInfo t)
+	docstring const deadkey(char_type c, KmodInfo const & t)
 		{ return trans_fsm_.currentState->deadkey(c, t); }
 	///
 	docstring const normalkey(char_type c)